Replacing a character from a certain index

Question

How can I replace a character in a string from a certain index  For example  I want to get the middle character from a string  like abc  and if the character is not equal to the character the user specifies  then I want to replace it   Something like this maybe   middle        I don t know how to get the middle of a string   if str middle     char      str middle  replace

User · Answer

As strings are immutable in Python  just create a new string which includes the value at the desired index   Assuming you have a string s  perhaps s    mystring   You can quickly  and obviously  replace a portion at a desired index by placing it between  slices  of the original   s   s  index    newstring   s index   1     You can find the middle by dividing your string length by 2 len s  2  If you re getting mystery inputs  you should take care to handle indices outside the expected range  def replacer s  newstring  index  nofail False         raise an error if index is outside of the string     if not nofail and index not in range len s            raise ValueError  index outside given string          if not erroring  but the index is still not in the correct range       if index  lt  0     add it to the beginning         return newstring   s     if index  gt  len s      add it to the end         return s   newstring        insert the new string between  slices  of the original     return s  index    newstring   s index   1     This will work as  replacer  mystring    12   4   myst12ing

User · Answer

You can t replace a letter in a string  Convert the string to a list  replace the letter  and convert it back to a string   gt  gt  gt  s   list  quot Hello world quot    gt  gt  gt  s   H    e    l    l    o         W    o    r    l    d    gt  gt  gt  s int len s    2      -   gt  gt  gt  s   H    e    l    l    o    -    W    o    r    l    d    gt  gt  gt   quot  quot  join s   Hello-World

User · Answer

You can also Use below method if you have to replace string between specific index def Replace Substring Between Index singleLine stringToReplace    startPos 0 endPos 1       try         singleLine   singleLine  startPos  stringToReplace singleLine endPos       except Exception as e          exception  quot There is Exception at this step while calling replace str index method  Reason    quot    str e          BuiltIn log to console exception      return singleLine

User · Answer

Use slicing to extract those parts of the original string to be kept s   s  position    replacement   s position length of replaced      Example  replace  sat  with  slept  text    The cat sat on the mat  text   text  8     slept    text 11     I P   The cat sat on the mat  O P   The cat slept on the mat

User · Answer

Strings in Python are immutable meaning you cannot replace parts of them   You can however create a new string that is modified  Mind that this is not semantically equivalent since other references to the old string will not be updated   You could for instance write a function   def replace str index text index 0 replacement          return   s s s   text  index  replacement text index 1      And then for instance call it with   new string   replace str index old string middle    If you do not feed a replacement  the new string will not contain the character you want to remove  you can feed it a string of arbitrary length   For instance   replace str index  hello bye  5    will return  hellobye   and   replace str index  hello bye  5  good     will return  hellogoodbye

[python] Replacing a character from a certain index

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